A recording of a chilling phone call between two men detailing their alleged plot to castrate Justin Bieber was aired for the first time yesterday.

“[Mark’s] going to strangle the pit bulls [Bieber and his guards], and you’re going to castrate them,’’ imprisoned murderer Dana Martin can be heard instructing Tanner Ruane, whose uncle, Mark Staake, also was allegedly in on it.

Martin — allegedly furious at Bieber for not answering his prison love letters — added of Bieber’s planned strangulation with a tie: “Tie it really, really tight. Knot it in the front once, really tight, put it in a knot. That cuts off the oxygen.’’

The recording, obtained by KOAT-TV in New Mexico, was made sometime before Nov. 28, the date of the planned attack, which was supposed to happen after a concert at Madison Square Garden.